Method and apparatus for forming fibrous webs



E. P. MILLER pril 12, 1949.

METHOD AND APPARATUS FOR FORMING FIBROUS WEBS 2 Sheets-Sheet 1 FiledNov. 23, 1946 JNVENTOR.

EMERY P. M ILLER April 1949- E. P. MILLER 2,466,906

METHOD AND'APPARATUS FOR FORMING FIBROUS WEBS Filed Nov. 23, 1946 2Sheets-Sheet 2 X INVENTOR. EMERY R MILLER BY 8W trode than its oppositeedge.

neutralized. Thereafter the mixed or coated particles are moved into asettling zone by the combined gas streams where the mixed or coatedparticles are subiectedto an electric field which charges and depositsthem on a belt in the form of matting or a web. The matting or webbuilds up its thickness progressively as it moves through the settlingzone. Preferably the electric field is created between a collectingelectrode and a depositing electrode spaced from each other and includesa plurality of vertical beams 21, a plurality of horizontal beams 28, alongitudinally I extending U-shaped member 29 mounted on theelectrically connected to a suitable high voltage source. The collectingelectrode may be in the form of a continuous metal mesh belt and pref-.

erably is pitched upwardly at an angle to the horizontal. The depositingelectrode comprises a series of fine wires or points arranged insubstantially one plane. The depositing electrode is spaced from thecollecting electrode so that the edge of the depositing electrodenearest the mixing'zone isfarther from the collecting elec- The purposeof this spacing is to reduce to a minimum the col-- lection. ofparticles on the depositing electrode prior to their becoming chargedand repelled by it. It also permits efficient deposition of theparticles over a greater effective area since the electrostaticdepositing force increases in the direction of movement of theparticles.

The improved electrostatic method and apparatus increases the efficiencyin forming the matting. This is so because the forces that exist in thesettling zone all act to force the I the collecting electrode, it ismoved out .of the settling zone for any further treatment desired andsubsequent removal from the belt.

For a better understanding of the invention,

together with other and further objects thereof,

reference is had to the following specification taken in connection withthe accompanying drawing, and. its scope will be pointed out intheappended claims.

In the accompanying drawing, Figure'l is a side elevation view of theapparatus;

Figure 2 is an end view taken along line 2-2 of the apparatus shown inFigure 1, and

Figure 3 is a top view taken along line 3-4 of the apparatus shown inFigure 1.

Referring now particularly to Figure i, there is shown a booth llsupported'on a plurality of insulators ii. The booth I0 is supported insuch a manner that its longitudinal axis is at an acute angle to thehorizontal. The booth comprises an open entrance 13, an open exit i4,side walls Ii and i6, ceiling i1 and fioor l8. The side walls ii and Iare preferably built so thatthey slant outwardly at an angle as shown inFigure 2. The fioor i8 is provided with an opening I! which extendscentrally and longitudinally thereof. Extending through the flooropening I! there is provided a supporting structure for a belt 20.

This supporting structure comprises a front pulley support 2i providedwith pulleys 22 and to one of the pulleys.

vertical members 21 and a plurality of rollers 30 which are iournaled inthe U-shaped member 28. The front pulley support 2i is located so thatits upper pulley 22 extends above the booth fioor I8 and is positionedintermediate the entrance and exit ends of the booth ii). The rearpulley support 24 is located outside of the booth in and beyond its exitend, and its upper pulley 25 is positioned to maintain the belt 20 abovethe booth floor it. The belt 20 is of the continuous type and is made ofconducting material, preferably of metal mesh so that it may serve asone electrode of an electric field. The belt is movably mounted totravel over the pulleys 22, 23, rollers 30 and pulleys 25, 26 in thedirection of the arrow shown in Figure 1. The movement of the belt isachieved by connecting a driving rnechanism ,(not shown) Since the beltand the various members of the belt supporting structure are maintainedat ground potential, they must be spaced at asuflicient distance fromother parts of the apparatus that are maintained at a differentelectrical potential to prevent sparkover.

A depositing electrode, generally indicated at 32 comprising arectangular frame 34 and a series of fine wires 2 stretched at equalintervals across the frame transversely of its length, is supported fromthe ceiling II by rods 33. The front edge of the electrode 22 is spacedfarther from the belt 22 than its rear edge. The electrode 22 as well asthe booth ll are connected to the negative terminal of a source of highvoltage 26. by a conductor 31.

Just outside the entrance it there are positioned a plurality of issuingmeans which in the drawing include a blower 40 and a pair of spray guns4i and 42. Preferably, the blower is positioned centrally of theentrance I; and the spray guns are positioned above and below theblower.

The discharge ends of both the blower 4| and the spray guns 4i and 42are surrounded by fine points or wires 43 for creating in these areas anionized atmosphere. The blower is electrically connected to the positiveterminal of a source of high voltage 44 by a conductor 45. The sprayguns 4| and 42 are connected to the negative terminal of the samevoltage source 44 by conductors 4i and 41. Voltage source 44 isconnected at its midpoint to ground by conductor 48.

The blower is connected to a source (not shown) of suitable fibrousmateriaLfor example, wood fibers, and is positioned to direct thismaterial into the booth Iii in a stream substantially parallel to thebelt 20. Each spray gun 4| and 42 is connected to a source (not shown)of suitable binding material, for example, a resin binder solution. Thesun 42 is positioned to direct a spray of the binding material upwardlyand toward the stream of fibrous material, and gun 4i is positioned todirect a spray of binding material downwardly and toward the stream offibrous material.

Consideringthe operation of the apparatus described, positively chargedfibrous particles are discharged into the booth Ill centrally of itsentrance and substantially parallel to its longitudinal axis.Simultaneously with the introduction of fibrous particles. spray guns 4iand 42 disll into which the fibrous and binding particles 7 r3 I? owninthe acc'diii Md conic rdtsihfldehc of ele ates-flawe c P e for""of'gravityperpendicularto the belt combine to propel. mixed clcsygntothe belt 20. That com I n'laiit of the gravitational force flcles and bsteixtqds zihsm mqifessu ptibl to the action of the field.

on the floor l8. Thereafter the belt carries this :ge improved mattingout of the booth l through a a t 4 its exit end. The web may thereafterbe given electrodesaid I Bing further treatment before use such, foexample, trically connected to said depositing and collectas pressingand drying, ing electrodes for creating an electrostatic field While thepresent in ti i of'cour not therebetween for depositing said mixedparticles restricted to any particular design, highly sati onto saidcollecting electrode after their entry factory results may be obtainedby using t into said settling zone and said depositing elecsign datalisted below in connection ith t trode being at a substantially greaterpotential embodiment described in this specification: than said ionizingmeans.

3. Apparatus for manufacturing matting commectmde of blower 501% Voltsprising a movable collecting electrode, a deposit- Elec des f Sp ay sing l tr d spaced from said collecting elec- II and 42 0,0 0 volts D. C.trode, high voltage source electrically con- Walls of booth I 1 Volts D.C- nected t said l t d srfor creating an electronepositing electmde v1t5static field between said electrodes, means for Belt 20 ro n Pot n l ltrostatically mixing particles of two differ p n between fmnt edge ofingredients of the matting, said means imparting electrode 32 and belt23 inches suflicient energy to said particles whereby they spacingbetween rear edge of move, after their mixture, into said electric fieldelectrode 32 and belt 20 17 inches for deposition on said collectingelectrode. Length of depositing electrode 9 feet 4. The invention .setforth in claim 3 with the By t invention superior mixing of t additionthat the edgefoi said depositing electrode gredient materials isobtained from which a web nefllfest 581d mixing means is pac t a e e ofimproved uniformity may be anufactur d distance from said collectingelectrode than its eiiiciently and economically. It will thus be seenOpposite edge. that there has been provided by this invention a 5. Theinvention set forth in claim 3 with the method and apparatus in whichthe various obaddition that said apparatus is arranged so that jectshereinbefore set forth together with many the precipitatingforce of saidelectrostatic field thoroughly practical advantages are successfully andthe forc of gravity make respectively an achieved. angle of ninetydegrees and an angle greater than Asvarious possible embodimentsmightbemade ninety degrees with the direction of movement of themechanical and electrical features oi the of the mixed particles as theyenter said field. above invention and as the art herein described 6. Inthe method of manufacturing matting, mi h be Varied in V rious parts allwithout dethe improvement which consists of electrostatim n f th s p fthe inv ntion, it is to cally mixing fibrous particles and binding parbeunderstood that all matter hereinbefore set ticl s and thereaftersubjecting said mixed parparticles into a matting.

'1. In the method of manufacturing the improvement which consists. ofelectrostatically coating fibrous particles with binding particles andthereafter subjecting the said coated particles to an electrostaticfield having ionizing characteristics for forming said particles into amatting by depositing them on a support.

8. The method of manufacturing matting which comprises imparting likeelectrical charges to the individual particles of one ingredient of thematting, imparting to particles of a second ingredient of the mattinglike charges of a polarity opposite to that of the charges on theparticles of said first ingredient, mixing said charged particles in acommon zone and presenting said mixed particles to an electrostaticfield for forming said particles into a matting.

9. The invention set forth in claim 8 with the addition that one of saidingredients comprises wood fiber particles and the other comprises aresin binder solution.

10. The method of manufacturing matting which comprises imparting likeelectrical charges to the individual particles of one ingredient of thematting, imparting to particles of a second ingredient of the mattinglike charges of a polarity opposite to that of the charges on theparticles of said first ingredient, imparting energy to said particlesfor moving them through first and second zones, said particles beingelectrostatically mixed in said first zone, and creating an ionizedatmosphere in said second zone for depositing said mixed particles upona support in the form of a matting. Y

11. A method of manufacturing matting which comprises mixing particlesof two diflerent ingredients by directing streams thereof toward eachother in a mixing zone and presenting said mixed particles to anelectrostatic field for forming said particles into a matting.

in the form of a mat.

512. In themethod of electrostatic depositing of particled adhesivematerial upon a base in a depositing zone, the improvement whichconsists in establishing an electrostatic field in the de positing zone,said field having an extended region in which field-intensityprogressively increases;

and introducing said material in a gas stream intosaid field region fromthe end thereof where the forces are the weakest. r

' 13. Apparatus for manuiacturing matting comprising a collectingelectrode, a depositing electrode spaced from said collecting electrode,a high voltage source electrically connected to said electrodes forcreating an electrostatic field therebetween, means forelectrostatically mixing particles oi. two different, ingredients foramatting. means for imparting suflicient energy to said particles formoving them, after their mixture, into said electrostatic field, andmeans for collecting the mixed particles in said il'eld EMERY P.LEILLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Date

